ACS Research Committee Report

SPERM WHALE SIZE ESTIMATED BY INTERVAL BETWEEN SOUND PULSES
Source: Rhinelander, M.Q. and S.M. Dawson. 2004. Measuring sperm whales from their clicks: Stability of interpulse intervals and validation that they indicate whale length. J. Acoust. Soc. Am. 115 (4): 1826-1831.

Sperm whale vocalizations consist mostly of short clicks, which function in echolocation. These sounds are produced by air being moved within an organ in the front of the snout, underneath the blowhole. Part of the sound radiates forward into the water, forming the first pulse of the click. The rest of the sound moves through the spermaceti organ in the head, until it reflects off the nasofrontal sac on the front of the skull. Then it passes again through the spermaceti organ and out into the water to form the second pulse. A portion of the sound energy is reflected again through the spermaceti organ, continuing the cycle until all the sound energy is used up. The interpulse interval is the time it takes for sound to pass through the spermaceti organ twice. This time is dependent on the speed of sound through spermaceti and the length of the spermaceti organ. The length of the spermaceti organ is correlated to the whale's overall length. In this study, 1997 recordings of sperm whale clicks in Kaikoura, New Zealand, were used for analysis of interpulse interval. The interpulse interval (IPI) was found to be different between almost all individuals. Also, within recordings from the same individuals, the IPI was different between years, potentially indicating growth during this period. The sperm whales in this study were also measured using photogrammetry and this measurement of length was found to have a higher variance than IPI length estimates. Finally, IPIs were significantly correlated to the photogrammetric measurements of sperm whale body size; therefore, the IPI seems to be an accurate method to estimate whale body size.    

BLOOD HORMONE LEVELS IN NORTH ATLANTIC MINKE WHALES
Source: Kjeld, M., A. Alfredsson, O. Olafsson, M. Tryland, I. Christensen, S. Stuen, and A. Arnason. 2004. Changes in blood testosterone and progesterone concentrations of the North Atlantic minke whale (Balaenoptera acutorostrata) during the feeding season. Can. J. Fish. Aquat. Sci. 61: 230-237.

North Atlantic minke whales, in contrast to many other baleen whales, seem to have a yearly reproductive cycle. Pregnancy rates are approximately 90-100% of sampled females; this is over 50% higher than in fin and sei whales. Minke whales migrate from high latitude feeding areas to warmer, lower latitude breeding areas during the winter. The gestation period is about 10 months and the lactation period is less than 6 months. Female minke whales do appear to become pregnant while nursing offspring. There is a rise in testosterone levels in sexually mature males during the feeding season; the same trend has been documented in fin whales. There is a weaker increase in progesterone levels in immature females during the same period. A rise in testosterone levels during the feeding season has been described for fin whales, as well. There also was a high progesterone level in the immature and mature, resting (non- pregnant, non-lactating) females. These levels are over five times higher than those for fin or sei whales during the same time of year. This difference is most likely because fin and sei whales reproduce every other year, rather than every year like the minke whales. Analysis of fetal length and male testosterone levels suggested that February is the peak month of conception for minke whales.    

NORTH PACIFIC RIGHT WHALE DISTRIBUTION, SHOWN BY WHALING RECORDS
Source: Clapham, P.J., C. Good, S.E. Quinn, R.R. Reeves, J.E. Scarff, and R.L. Brownell, Jr. 2004. Distribution of North Pacific right whales (Eubalaena japonica) as shown by 19th and 20th century whaling catch and sighting records. J. Cetacean Res. Manage. 6 (1): 1-6.

North Pacific right whales were hunted from 1835 and were already depleted in numbers throughout their range by 1900. At this time, commercial whaling efforts shifted towards other species. There were still occasional reported catches of right whales in the early 1900s. Whalers from the Soviet Union illegally killed at least 508 North Pacific right whales between the 1950s and 1970s. This illegal hunt devastated the recovery of the western and, to a greater degree, the eastern North Pacific right whales. This study compiled whaling records to compare right whale distribution in the 1800s and 1900s. Whaling data demonstrated that almost all of the Gulf of Alaska, plus the coast of British Columbia, the Alaska Peninsula, and the southeastern Bering Sea were used as summering grounds for right whales. In addition, right whales in the western North Pacific used the Sea of Japan, which in modern days has virtually no sightings. In general, right whale distribution was greater during the 1800s than in modern times. The remaining right whales in the North Pacific appear to make up two discrete populations- eastern and western. The western population size is unclear, but it is believed to be larger, perhaps in the hundreds, than the eastern population, which may number only in the tens of animals. There are seasonal changes in distribution evident in the whaling data. There were few sightings of right whales in either offshore or nearshore waters from November to February. In March, most sightings were in the mid latitudes. By April, right whales moved into the Bering Sea and from May through August, there were many sightings in the Bering Sea and the Gulf of Alaska. In September, there was a general southward movement, with the last right whales leaving the Bering Sea in October to head back to the mid latitudes. In general, right whales demonstrated a migration north in spring and south again in autumn.    

FOOD SHARING IN WILD BOTTLENOSE DOLPHINS
Source: Fedorowicz, S.M., D.A. Beard, and R.C. Connor. 2003. Food sharing in wild bottlenose dolphins. Aquatic Mammals 29 (3): 355-359.

Two bottlenose dolphins in Golfo Dulce, Costa Rica, were documented food sharing, a very rare mammalian behavior. The fish was shared between a male and a female accompanied by a calf for 30 minutes. Possession of the fish alternated 11 times between the male and female. Consumption of the fish did not seem to begin until possession had changed several times. The exact relationship between the male and female is unknown, but there was an observation of sexual behavior between the pair on the previous day.    

FLIPPER TUBERCLES AFFECT UNDERWATER MOVEMENTS OF HUMPBACK WHALES
Source: Miklosovic, D.S., M.M. Murray, L.E. Howle, and F.E. Fish. 2004. Leading-edge tubercles delay stall on humpback whale (Megaptera novaeangliae) flippers. Physics of Fluids 16 (5): 39-42.

Most baleen whales are relatively inflexible in most of their bodies; however, humpback whales are capable of conducting elaborate turning maneuvers while feeding. This species utilizes their long, flexible flippers in many of these maneuvers. Humpback flippers, unlike those of other species, have large, rounded tubercles along their leading edge. The placement, size, and number of tubercles on humpback flippers seem to be analogous to leading edge control devices used in engineering. This study used scale models of humpback whale flippers (both with and without tubercles) in a wind tunnel in order to determine the effect of tubercles on hydrodynamic characteristics. The tests determined that the tubercles serve to delay stall at higher flipper angle by providing more lift and decreasing drag. This characteristic would be advantageous for the humpback whale during feeding activities. For instance, angling one flipper to increase lift and one flipper to decrease lift would provide the ability to roll or make tight turns quickly. Conversely, the same angle from both flippers would create maximum lift and, therefore, facilitate fast descents or ascents.